ENDOCRINE - Calcium And Vit D Flashcards
Why is 40% of plasma calcium inactive?
Because it is bound to albumin
If someone has low albumin, how will their non-adjusted calcium appear?
Low
Effect on acidotic states on ionized Ca2+ ( why)
Increase Ca2+
By decreasing albumin binding
Effect on alkalotic states on Ca2+ (ionized) + why
Decreased ionized Ca2+
By increasing albumin binding
WHere are the Parathyroid glands
Lying posterior to the thyroid
Which cells secrete Parathyroid hormone (PTH)
Chief cells
When is PTH secreted (3)
When plasma Ca = low
If Vit D = low
If PO4 = high
3 ways in which PTH increases plasma Ca levels
Directly stimulating Ca reabsorption from bone
Directly increasing renal tubular Ca reabsorption
Indirectly stim incr GI Ca absorption (by incr Vit D activation kidney)
Secondary effect of PTH
Increases renal PO4 excretion
Affect of Vit D on Ca + PO4 levels
Sustains/increases both by increasing inflow from GIT
How is Vit D synthesised endogenously
In kin —> D3 (cholecalciferol)
How is Vit D ingested exogenously
As D2 - ergocalciferol
Where does 1st hydroxylation of Vit D take place
Liver
Where does 2nd hydroxylation of Vit D take place
Kidneys = active form
Where is calcitonin secreted
Parafollicular C cells of thyroid gland
What is Calcitonin secreted in response to
High levels of Ca
How does Calcitonin decrease Ca
Antagonism of effect of PTH on bone
What is 90% of renal excretion of Ca related to
Sodium reabsorption PCT
What is the other 10% of Ca renal excretion related to
PTH regulation in the distal tubule
WHat is 97% of hypercalcaemia due to?
1’ hyperPTH or malignancy
Distinguishing 1’hyperPTH from malignancy
PTH high in 1’hyperPTH
PTH low In malignancy + Ca much higher
Causes of hypercalcaemia
XS PTH secretion - 1/3’hyperPTH + ectopic PTH secretion
Myeloma
Mets deposits in bone
Paraneoplastic - PTHrp (SCC)/Production of osteoclasts factors
XS Vit D - exogenous, TB/Sarcoid/ lymphoma
Milk-alkali syndrome
Thyrotoxicosis
Addisons
Severe AKI
Sx - thiazides diuretics, Li
Familial hypocalcicuric hypercalcaemia
What is 80% of 1’hyperPTH due to
Parathyroid adenomas
What are the other 20% of 1’hyperPTH due to?
Diffuse hyperplasia of all glands (e.g. as part of MEN1/2a)
PTH and Ca2+ levels 1’hyperPTH
Ca2+ + PTH high
Tx 1’hyperPTH
Parathyroidectomy
Is parathyroidectomy indicated in asymptomatic 1’hyperPTH
YES
Because of potential LT adverse effects
After parathyroidectomy, how long does it take for ca2+ to be norm again
24hrs
Complication parathyroidectomy + how. To prevent it
Hypocalcaemia
Give 14 days AdCal post op
What is 2’hyperPTH
Physiological hypertrophy of all PT glands due to hypocalcaemia
Which conditions can cause 2’hyperPTH (2)
Renal disease
Vit D deficiency
2’hyperPTH - Ca + PTH levels
PTH high
Ca low/norm
Tx 2’hyperPTH
Tx cause
What is 3’hyperPTH due to
Long standing 2’ hyperPTH esp in renal failure
Ca/PO4/PTH levels 3’hyperPTH
Ca high
PTH high
PO4 very high q
Tx 3’hyperPTH
Parathyroidectomy
Sx 1’hyperPTH (5)
Usually asymp. If Sx: BONES STONES ABDO GROANS PSYCHIC MOANS
Bone Sx 1’hyperPTH (3)
Bone pain
Pathological fractures
Mm weakness
Stone Sx 1’hyperPTH
Renal stones
Polyuria
AKI/CKD
Abdo groans Sx 1’hyperPTH (5)
Abdo pain Vomiting Constipation Pancreatitis GI ulcers
Psychic moans Sx 1’hyperPTH/hyperCa (4)
Depression
Confusion
Tiredness
Hypotonicity
ECG changes 1’hyperPTH/hypercalcaemia
Reduced QT interval —> cardiac arrest
Ix 1’hyperPTH (8)
PTH raised Ca raised PO4 reduced ALP raised 24 urinary Ca raised DXA scan - extent of OP Technetium scan - tumour localisation USS - tumour localisation
Why do we do 24h urinary Ca in Ix 1’hyperPTH
To rule out familial hypocalciuric hyerpcalcaemia
Classical XR changes 1’hyperPTH
Hand XR - classic subperiosteal bone resorption
Men 1 - 3 Ps
Parathyroid hyperplasia/adenoma
Pancreatic endocrine tumours - gastronomy/insulinoma
Pituitary adenoma
Men 2a - TAP
Thyroid - medullary carcinoma
Adrenal PCC
Parathyroid hyperplasia
Men 2b
MEN2+ mucosal neuromas + Marfanoid appearance
No hyperPTH
When to Tx hypercalcaemia
If >3.5 + severe Sx
Tx hypercalcaemia
3-6L 0.9% NaCl over 24h
Disphosphonates - 1 dose pamidronate
When to use calcitonin in Mx hypercalcaemia
Life threatening hypercalcaemia as rapidly reduces Ca
When to use dialysis in Mx hypercalcaemia
If renal impairment
When to use steroids in mx hypercalcaemia
If hypercalcaemia = due to myeloma, lymphoma or sarcoid
When may hypocalcaemia be an artefact?
If low serum albumin is not corrected
Causes of hypocalcaemia w/ low PTH (DiGeorge says HIIIII)
Digeorge syndrome Severe Hypomagnesia Idiopathic (1'hypoPTH) autoImmune Iatrogenic - post thyroid/parathyroid surgery post neck Irradiation Infiltration - sarcoid/malignancy
Causes of hypocalcaemia w/ high PTH
Dick and Vagina always relieve Robs anal tension Dx - bisphosphonates/calcitonin Acute Hyperphosphataemia Vit D defcieincy Alkalosis Renal failure Rhabdomyolysis Acute pancreatitis Tumour lysis
S+S hypocalcaemia (10)
Peripheral irritability Tetany/cramps Trosseau's sign Chvostek's sign Central irritability Seizures Depression/anxiety Perioral parasethesia Cataracts
What is Trosseau’s sign
Wrist flexion + fingers drawn together
Esp after occlusion of brachial aa ie BP cuff
Hypocalcaemia
What is Chvostek’s sign
Tapping over facial nn causes twitches
Hypocalcaemia
Ix hypocalcaemia (5)
Se Ca = low Se PTH = low or high Check Parathyriod ab if low Se Vit D ECG - prolonged QT
Mx mild-mod hypocalcaemia
AdCal
Mx severe hypocalcaemia (2)
Ca gluconate IV 10ml 10% bolus then maintenance infusion
AdCal ASAP
